1. Field of the Invention
A refrigerant recovery system for use in combination with a low pressure recovery reservoir to recover refrigerants such as CFC, HCFC and HFC.
2. Description of the Prior Art
Numerous efforts have been made to design and configure systems to recover refrigerants from refrigeration and air conditioning systems.
U.S. Pat. No. 5,617,731 teaches a refrigerant recovery/recyclying apparatus including a primary vapor-type filter/dryer to receive recovered vapor refrigerant with isolation valves upstream and downstream thereof so as to allow replacement of the cores. To prevent excessive inlet pressures to the compressor of the recovery apparatus, a crankcase pressure regulator is provided upstream of the compressor inlet. In addition, an oil separator removes compressor oil from the superheated vapor refrigerant emerging from the compressor and returns the oil to the compressor through a return line. Condensed liquid refrigerant is provided to the recycling apparatus of the system by first passing through a second or recirculation filter/dryer. The filtered liquid refrigerant, from which non-condensable gas has been effectively removed by agitation in the filter/dryer, can then be supplied to an internal or external tank and recycled through a hand expansion valve which throttles the liquid refrigerant into a vapor phase over a continuous range.
U.S. Pat. No. 5,537,836 shows a refrigerant recovery unit including four distinct refrigerant flow paths automatically controlled to perform four separate and distinct functions. In a liquid refrigerant path, liquid refrigerant is recovered from the discharge side of an idle unit through the refrigerant recovery unit by use of the differential pressure between the disabled unit and the refrigerant receiving can. In a primary vapor path, evacuation of gaseous refrigerant from the high and low sides of the idle unit is achieved by use of a compressor in the recovery unit which produces a differential pressure to induce flow. This differential pressure is produced solely by the recovery unit compressor until such time as the intake pressure of the compressor reaches approximately 4 inches Hg. vacuum. When the compressor intake pressure reaches 4 inches Hg. vacuum, the system automatically switches to a secondary vapor path for recovering gaseous refrigerant from the high and low side of the idle unit by sequencing an external vacuum pump in series with the compressor of the recovery unit to produce the differential pressure inducing flow. This differential pressure is continued until the intake pressure reaches a desired vacuum level of up to 29.9 inches Hg. Finally, to recover gaseous refrigerant or non-condensible gas from the high and low side of the idle unit after the desired vacuum level has been reached, differential pressure is obtained by connecting the external vacuum pump through the recovery unit without using the compressor.
U.S. Pat. No. 5,671,605 relates to a refrigerant recovery system for recovering refrigerant from a cooling system. An oil separator separates oil from refrigerant before the refrigerant is drawn into the compressor. The oil separator has a helical coil disposed in a heat exchange relationship with the oil separator for receiving the refrigerant after the refrigerant is compressed by the compressor to cool the refrigerant. A condenser coil is also provided for receiving the refrigerant after the refrigerant has passed through the helical coil to further cool the refrigerant causing the refrigerant to condense.
U.S. Pat. No. 5,582,023 discloses a portable apparatus for recovering refrigerant from a refrigeration system and delivering the refrigerant to a refrigerant storage tank. The apparatus includes a liquid sensing thermistor in contact with the refrigerant entering the recovery machine. When liquid is detected, the refrigerant is routed directly to the recovery tank. Gaseous refrigerant and any non-condensable gases from the top of the recovery tank are directed to the suction of a compressor and then to a condenser and to a purge vessel that functions as a receiver. When the entering refrigerant is in a gaseous phase, the refrigerant is routed to the suction of the compressor. A second liquid sensing thermistor is in contact with the gaseous refrigerant from the top of the recovery tank and if liquid is detected the recovery process is terminated. A liquid sensing device near the bottom of the purge vessel actuates a solenoid valve to return the condensed liquid to the liquid inlet of the recovery tank. A cooling coil at the interior top of the purge vessel also condenses refrigerant. When non-condensable gases accumulate around the coil, there is less latent heat input to the coil and the suction line temperature drops. A temperature control with the sensing bulb at the suction line at a preset point actuates a solenoid valve in a line from the top of the purge vessel to purge the non-condensable gas through a small orifice to the atmosphere.
U.S. Pat. No. 5,597,533 shows an apparatus to sample and analyse refrigerant for purposes of refrigerant recovery and reuse including a refrigerant cell having a chamber for containing a refrigerant sample and a passage for connecting the chamber to a source of refrigerant in vapor phase. The sample chamber and passage are evacuated, and the chamber and at least a portion of the passage contiguous with the chamber are cooled until the temperature thereof reaches a predetermined temperature at or below ambient temperature. After the chamber and passage have been evacuated and cooled, the passage is connected to a source of refrigerant in vapor phase such that a refrigerant vapor sample is drawn into the chamber and condensed to liquid phase. After the cell chamber has been filled with a liquid refrigerant sample, one or more desired properties of the liquid refrigerant sample are measured or detected.
U.S. Pat. No. 5,533,345 and U.S. Pat. No. 5,537,835 disclose a system for transferring a refrigerant from a first refrigerant vessel having at least one refrigerant port to a second refrigerant vessel having at least one refrigerant port. This system includes a condenser, a pump assembly having an inlet and an outlet and conduits for operatively connecting the condenser and pump assembly to the first and second refrigerant vessel in several configurations. The pump assembly includes two pumps operated by one motor and interconnected to either provide series or parallel pumping. This system may also include a transfer tank interposed between the first and second refrigerant vessels. The transfer tank can be used to condense the vapor phase of the refrigerant removed from the first refrigerant vessel and collect the condensed refrigerant in one configuration, then to transfer the condensed refrigerant to the second refrigerant vessel in an alternate configuration. Methods employing this apparatus for transferring a refrigerant between a first refrigerant vessel and a second refrigerant vessel, optionally through a separate transfer tank, are also disclosed.
Despite these efforts to provide efficient, cost effective refrigerant recovery devices there remains a need for a rapid affordable refrigerant recovery system.